The present invention relates to door opening devices and, in particular, to a device for releasing the latch on a latched door so that the door can be moved from the closed position to the open position without interference from the latch.
In my prior U.S. Pat. No. 5,634,296 I disclosed a device which can be connected between a door and a wall for opening and closing the door. Although the device will reliably move the door between an open position and a closed position, where the door has a latch, the door must also be fitted with some form of latch release. Existing latch releases operate by releasing the latch plate in the wall. Although such latch releases work effectively, they are difficult to install because costly modifications are needed to accommodate the releasable latch plate, and the release solenoid draws conventional AC power such that the device must be wired into the electrical system of the structure.
It would be desirable to provide a latch release device which would not require modifications to the door frame and that would not have to be connected into the AC electric system servicing the structure.
Briefly, the present invention is embodied a device for unlatching a door which is latched into a door frame where the door latch assembly includes an elongate lever arm rotatable about an axis from a first latched orientation to a second unlatched orientation. The device is attachable to the door and includes a cable having a first end attachable to the distal end of the lever arm and a second end attached to a take up spool. The take up spool is rotated by a motor in a first direction to take up the cable and thereby draw the lever arm from the first latched orientation to the second unlatched orientation and thereafter rotate in the second direction to release the cable and allow the lever arm to return from the second unlatched orientation to the first latched orientation.
The device includes a first detector for detecting when the spool has rotated in a first direction until the lever arm has been drawn to the second orientation, a second detector for detecting when the spool has rotated in the second direction until the lever arm has returned to the first orientation, a third detector for detecting when the door has moved out of the frame, and a start means for starting the unlatching sequence. A logic, which may be in the form of a microprocessor, is responsive to the first detector, the second detector, the third detector, and the start means and directs power to the motor for rotating the spool in the first direction upon actuation of the start means, terminates power to the motor to stop rotation of the spool in the first direction upon receipt of a signal from the first detector, commences power to the motor to rotate the spool in the second direction upon receipt of the signal from the third detector, and terminates power to the motor to stop rotation of the spool upon receipt of a signal from the second detector.
In the preferred embodiment, the first and second detectors comprise cams mounted on the shaft of the spool which engage associated limit switches. The third detector may be any of a number of known devices for detecting when a door has moved out of a closed position, includes detectors associated with door opening devices or a device for assisting in moving a door from a closed orientation to an ajar orientation as disclosed in my patent application filed on Jul. 28, 1999 as Ser. No. 09/362,248.